Hazardous waste disposal has become more difficult as stricter solid waste disposal and air emissions standards have been implemented. In petrochemical and crude oil refining, both liquid wastes and solid wastes are generated which must be safely and economically treated to alleviate the hazards associated with the waste streams. Since there is often an inherent fuel value associated with many refinery wastes streams, disposal procedures have been developed to burn such waste stream fuels in furnaces and kilns in order to recover the fuel value, while reducing both the nature and volume of the waste stream from large volumes of complex organic molecules to simple carbon dioxide and water combustion products. This form of waste utilization reduces the volume of the original waste stream. It also degrades the hazardous molecules to environmentally acceptable products.
The disposal of solid waste products generated during petroleum refining poses an even more challenging opportunity. These solid wastes are diverse, having been generated in filtering, reactor processing and settling process steps. Sometimes, the solids are metal salts requiring special disposal techniques. Often, these solid materials are coated or infiltrated with hydrocarbon molecules, making their disposal more complex, and their retention in hazardous waste disposal sites expensive.
The present invention provides fuel compositions and methods of making such fuels whereby certain refinery waste streams having adequate fuel value are advantageously combined with refinery solid wastes to obtain a fuel for use in cement kilns. The cement kiln provides a process environment in which high kiln temperatures insure adequate degradation of the heavy organic molecules. Simultaneously, the cement kiln provides a matrix of solid cement particles which are chemically compatible with the solid particles resulting from the refinery solid wastes so as to obtain an acceptable cement product.
Fuels made according to the present invention must meet several criteria in order to qualify as cement kiln fuels. The two most important specifications are that the fuel containing solids must be pumpable in varying outdoor temperatures, and it must provide adequate fuel value so that high temperatures can be maintained in the cement kiln. Both of these criteria are in conflict with the refiner's objective of disposing of the maximum mass of waste solids in the lowest fuel value stream. These disparate factors are satisfactorily resolved in the present invention which provides for fuels with high solids content and adequate fuel value for cement kiln applications.